X-ray inspection devices have conventionally been in use to detect foreign matter (such as metal, glass, shells, bones, etc.) mixed in an examination subject article, for example, food. Generally, an X-ray detection device for foreign matter has a configuration in which examination subject articles being conveyed by conveyance means are sequentially examined. For the conveyance means to be used, a type of means suitable for the type of the examination subject articles is selected.
For example, to convey foodstuff such as stripped shellfish like stripped short neck clams, fish paste, retort food materials, and soup with fillings, a pipeline and means for moving an examination subject article in the pipeline, for example, a pump are used. When the examination subject article to be conveyed in the pipeline includes solid materials such as stripped short neck clams or retort food materials, they are fluidly conveyed in the pipeline together with a conveyance fluid (for example, water). When the examination subject article to be conveyed in the pipeline includes fluid materials or solid materials mixed with a fluid such as fish paste or soup with fillings, the examination subject article is fluidly conveyed as it is in the pipeline using no conveyance fluid.
An example of an X-ray detection device for foreign matter using a pipeline as conveyance means as described above is disclosed in Patent Reference 1 (Japanese Patent Laid-Open No. 2591171). The X-ray detection device has, as shown in FIG. 8, an X-ray detection section 116 to which an examination subject article (including a stripped shellfish 110, foreign matter such as shells and metal pieces, and a conveyance fluid 112) is supplied from a supply tank, not shown, through a pipeline 114. In the X-ray detection section 116, the examination subject article is irradiated, at a prescribed timing, with X-rays emitted from an X-ray generation tube 118 through a pipeline 120 communicated to a downstream portion of the pipeline 114. Then, X-rays having penetrated the examination subject article are measured at constant intervals by plural X-ray sensors 122 and plural X-ray sensors 124. The X-ray sensors 122 and the X-ray sensors 124 are respectively arranged in a direction crossing the pipeline 120.
When a foreign matter detection signal is outputted from a signal processing section, not shown, based on the results of measurement by the X-ray sensors 122 and 124, a discharge valve 128 is operated to guide the portion containing foreign matter of the examination subject article into a pipeline 130 for discharge.
The upstream pipeline 114 is made of a stainless steel pipe (SUS pipe) and the downstream pipeline 120 is made of a resin pipe which is X-ray transmissive.
To check and adjust the foreign matter detection sensitivity of the above X-ray detection device for foreign matter, test pieces are used. When checking and adjusting the detection sensitivity, plural kinds of test pieces are prepared according to the kinds and sizes of foreign matter expected to be detected. The test pieces thus prepared are made to flow, together with a fluid, in the pipeline at speed similar to the flow speed used in real detection operation and are irradiated with X-rays under conditions similar to those under which real detection operation is carried out. By doing so, what sizes of test pieces can be detected under the conditions can be determined, so that it becomes possible to adjust and determine, for the size of foreign matter to be detected, the conditions (for example, fluid velocity in the pipeline and the intensity of X-rays) under which detection operation is to be carried out.
As described above, to check the foreign matter detection sensitivity of an X-ray detection device for foreign matter used to detect foreign matter mixed in an examination subject article being fluidly conveyed in a pipeline, it is necessary to carry out checking by actually flowing test pieces in the pipeline. To carry out such checking, the pipeline requires to be provided with an appropriate inlet at its front stage, which complicates the device configuration. Furthermore, since test pieces different from an examination subject article are put in the pipeline every time such checking is carried out, it is necessary to clean inside the pipeline after the checking. This leads to a problem of making operation troublesome.
The present invention solves the above problems. An object of the present invention is to provide an X-ray detection device for foreign matter provided with a mechanism which allows the sensitivity of foreign matter detection by use of X-rays to be checked by using a simple configuration and performing simple operation without requiring test pieces to be mixed in an actual examination subject article.